The present invention relates to an antenna device having a feed circuit that composes a plurality of beams in an array antenna which is arranged circumferentially.
A conventional antenna device will be described with reference to the accompanying drawings. FIG. 9 is a diagram showing the structure of a conventional antenna device which is disclosed, for example, in Japanese Patent Laid-Open No. 61-169002.
Referring to FIG. 9, reference symbol 2 denotes an entire feed circuit; E0, E1, E2, E3 and E4 are antenna elements; H2 is a 180-degree hybrid; Dm is a reflection free termination; Ac is an amplitude adjuster; Pc is a phase compensating circuit; H1 is a 90-degree hybrid; Pb is a four-division divider; and F1, F2, F3 and F4 are feed terminals.
Then, the operation of the conventional antenna device will be described with reference to the accompanying drawings.
When an electricity is fed to the feed terminal F1 by the hybrids H1, H2, the phase compensating circuit Pc and the amplitude adjuster Ac, the excitation amplitude phases of ja, exp(jp(xcfx89), xe2x88x92exp(jp(xcfx89)), j(1xe2x88x92a/2)A(xcfx89), and j(1xe2x88x92a/2)A(xcfx89) are fed to the five antenna elements E0, E1, E2, E3 and E4, respectively.
Similarly, when an electricity is fed to the feed terminal F2, the excitation amplitude phases of ja, j(1xe2x88x92a/2)A(xcfx89), j(1xe2x88x92a/2)A(xcfx89), exp(jp(xcfx89)), and xe2x88x92exp(jp(xcfx89)) are fed to the five antenna elements E0, E1, E2, E3 and E4, respectively.
Similarly, when an electricity is fed to the feed terminal F3, the excitation amplitude phases of ja, xe2x88x92exp(jp(xcfx89)), exp(jp(xcfx89)), j(1xe2x88x92a/2)A(xcfx89), and j(1xe2x88x92a/2)A(xcfx89) are fed to the five antenna elements E0, E1, E2, E3 and E4, respectively.
Similarly, when an electricity is fed to the feed terminal F4, the excitation amplitude phases of ja, j(1xe2x88x92a/2)A(xcfx89), j(1xe2x88x92a/2)A(xcfx89), xe2x88x92exp(jp(xcfx89)), and exp(jp(xcfx89)) are fed to the five antenna elements E0, E1, E2, E3 and E4, respectively.
With the above operation, the feed points of the feed terminals F1, F2, F3 and F4 are changed over, to thereby change over the beams of four kinds so as to conduct the transmit/receive of the signal.
In the above-mentioned conventional antenna device, in order that the four antenna elements E1 to E4 which are arranged circumferentially and the antenna element E0 of one element which exists in the center thereof are excited to form the four kinds of beams, the twelve 90-degree hybrid circuits H1, the four 180-degree hybrid circuits H2, the four amplitude adjusters Ac, the four phase compensating circuits Pc and the four-division divider circuits Pb must be connected in multiple stages.
For example, even in the case where the array structure is made up of only four elements which are arranged circumferentially except for the one element which is disposed in the center of a circle, the four-division divider circuit Pb is merely removed. Therefore, there arise such problems that hardware becomes complicated, a connection loss becomes large and a signal to noise ratio (hereinafter referred to as xe2x80x9cSN ratioxe2x80x9d) is deteriorated.
The present invention has been made in order to solve the above-mentioned problems, and therefore an object of the present invention is to obtain an array antenna device which is capable of forming plural kinds of beams by a simple feed circuit structure in an array antenna which has four antenna elements which are arranged circumferentially and have a diameter which is uneven times of the half wavelength as a unit.
An antenna device according to claim 1 of the invention includes: first, second, third and fourth antenna elements which are arranged circumferentially at regular intervals; a first 90-degree hybrid having first, second, third and fourth terminals; a second 90-degree hybrid having fifth, sixth, seventh and eighth terminals; a third 90-degree hybrid having ninth, tenth, eleventh and twelfth terminals, and a fourth 90-degree hybrid having thirteenth, fourteenth, fifteenth and sixteenth terminals, in which: the third terminal of the first 90-degree hybrid and the ninth terminal of the third 90-degree hybrid are connected to each other; the fourth terminal of the first 90-degree hybrid and the thirteenth terminal of the fourth 90-degree hybrid are connected to each other; the seventh terminal of the second 90-degree hybrid and the tenth terminal of the third 90-degree hybrid are connected to each other; the eighth terminal of the second 90-degree hybrid and the fourteenth terminal of the fourth 90-degree hybrid are connected to each other; the eleventh terminal of the third 90-degree hybrid and the first antenna element are connected to each other; the twelfth terminal of the third 90-degree hybrid and the second antenna element are connected to each other; the fifteenth terminal of the fourth 90-degree hybrid and the third antenna element are connected to each other; the sixteenth terminal of the fourth 90-degree hybrid and the fourth antenna element are connected to each other; the passing phases of from the first terminal of the first 90-degree hybrid to the fourth terminal, from the second terminal to the third terminal, from the fifth terminal of the second 90-degree hybrid to the eighth terminal, from the sixth terminal to the seventh terminal, from the ninth terminal of the third 90-degree hybrid to the twelfth terminal, from the tenth terminal to the eleventh terminal, from the thirteenth terminal of the fourth 90-degree hybrid to the sixteenth terminal, and from the fourteenth terminal to the fifteenth terminal are set to 0 degree; and the passing phases of from the first terminal of the first 90-degree hybrid to the third terminal, from the second terminal to the fourth terminal, from the fifth terminal of the second 90-degree hybrid to the seventh terminal, from the sixth terminal to the eighth terminal, from the ninth terminal of the third 90-degree hybrid to the eleventh terminal, from the tenth terminal to the twelfth terminal, from the thirteenth terminal of the fourth 90-degree hybrid to the fifteenth terminal, and from the fourteenth terminal to the sixteenth terminal are set to 180 degrees.
An antenna device according to claim 2 of the invention includes: first, second, third and fourth antenna elements which are arranged circumferentially at regular intervals; a first 180-degree hybrid having first, second, third and fourth terminals; a second 180-degree hybrid having fifth, sixth, seventh and eighth terminals; and a third 180-degree hybrid having ninth, tenth, eleventh and twelfth terminals, in which: the third terminal of the first 180-degree hybrid and the fifth terminal of the second 180-degree hybrid are connected to each other; the fourth terminal of the first 180-degree hybrid and the ninth terminal of the third 180-degree hybrid are connected to each other; the seventh terminal of the second 180-degree hybrid and the first antenna element are connected to each other; the eighth terminal of the second 180-degree hybrid and the second antenna element are connected to each other; the eleventh terminal of the third 180-degree hybrid and the third antenna element are connected to each other; the twelfth terminal of the third 180-degree hybrid and the fourth antenna element are connected to each other the passing phases of from the first terminal of the first 180-degree hybrid to the fourth terminal, from the second terminal to the third terminal, from the fifth terminal of the second 180-degree hybrid to the eighth terminal, from the sixth terminal to the seventh terminal, from the ninth terminal of the third 180-degree hybrid to the twelfth terminal, and from the tenth terminal to the eleventh terminal are set to 0 degree; and the passing phases of from the first terminal of the first 180-degree hybrid to the third terminal, from the second terminal to the fourth terminal, from the fifth terminal of the second 180-degree hybrid to the seventh terminal, from the sixth terminal to the eighth terminal, from the ninth terminal of the third 180-degree hybrid to the eleventh terminal, and from the tenth terminal to the twelfth terminal are set to 180 degrees.
An antenna device according to claim 3 of the invention further includes in the above-mentioned antenna device according to claim 1, a signal processing unit that composes beams by multiplying a complex excitation amplitude whose amplitude is in proportion to the amplitudes of the signals which are received at the first and second terminals of the first 90-degree hybrid and the fifth and sixth terminals of the second 90-degree hybrid, and whose phase is the inversion of the signs of the phases of the signals of the first and second terminals of the first 90-degree hybrid and the fifth and sixth terminals of the second 90-degree hybrid.
An antenna device according to claim 4 of the invention further includes in the above-mentioned antenna device according to claim 1, a signal processing unit that directs a main beam in an arrival direction of a desired signal and forms a zero point of the directivity of the beam in an arrival direction of an interference signal on the basis of the signals which are inputted from the first and second terminals of the first 90-degree hybrid and the fifth and sixth terminals of the second 90-degree hybrid.